Cholinergic modulation of neural activity in the telencephalon of the zebrafish

In this study, we have assessed the effects of muscarinic receptor activation on neural activity in the telencephalon of the zebrafish. Electrically evoked field potentials via the stimulation of the posterior dorsal telencephalon were recorded in the anterior dorsal telencephalon of the ipsilateral hemisphere, with a peak latency of 20-30 ms. The application of carbachol (1-25 μM) and oxotremorine-M (0.25-60 μM) suppressed the amplitude of field potentials in a dose-dependent manner. This suppressive effect was blocked by a muscarinic receptor antagonist, atropine (20 μM), and an M1 receptor antagonist, pirenzepine (5 μM), but not by the M2 receptor antagonists, methoctramine (5 μM) and gallamine (5 μM). Oxotremorine-M (1 μM) also suppressed the induction of field potentials via the stimulation of the contralateral telencephalon and the medial fiber bundle, which was blocked by atropine (20 μM). An acetylcholine esterase inhibitor, physostigmine (20-30 μM), reduced the peak amplitude of the evoked field potentials, while increasing late bursting activity. Furthermore, a high dose of physostigmine (100 μM) induced spontaneous bursting activity. These results demonstrated the cholinergic influence on the neural activity in the telencephalon of the zebrafish.